Cold-die hot-press forming die and method for preparing thermoplastic composite

Abstract

The present application relates to a kind of cold mold-hot press forming die and thermoplastic composite preparation method, belong to composite material forming technical field.The die includes upper die and lower die, and upper die and lower die are respectively provided with opposite upper die forming surface and lower die forming surface;The side of upper die forming surface is sequentially provided with upper die heating part, upper die heat insulation part and upper die cooling part, heating element and first medium flow channel are arranged in upper die heating part, second medium flow channel is arranged in upper die cooling part, first medium flow channel and second medium flow channel are communicated by upper die control pipeline, and upper die control pipeline is arranged in upper die heat insulation part and is provided with valve assembly;Lower die is symmetrically arranged with upper die.When heating part is at high temperature and cooling part is at low temperature, heat exchange between the two can be prevented by heat insulation part and valve assembly in heat insulation part, so that heat transfer in the direction of blank of heating part is maintained during heating process, and valve assembly is opened when cooling, low-temperature medium can be transported into heating part to realize rapid cooling of the die.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, specifically relating to a cold mold-hot pressing molding die and a method for preparing thermoplastic composite materials. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Thermoplastic composite components can be manufactured using autoclave or hot press (hot mold hot press) processes. However, prepreg laying requires high temperatures and the prepreg is highly viscous, making operation difficult. In addition, both the mold and the blank need to be preheated. The mold consumes a lot of energy during the entire heating process. The heat dissipation of the hot mold hot press mold needs to be achieved through natural heat dissipation or air cooling in the closed state, which results in low cooling efficiency and low production efficiency.

[0004] In contrast, in hot mold cold pressing technology, a room-temperature blank is placed into a preheated mold, the mold is closed and heated, and then pressed and cooled. No additional heating is applied during the pressing process; instead, the heat from the mold is transferred to the pressed component, thus cooling the mold. However, due to the limited heat storage capacity of the mold, insufficient heating may occur when preparing thick-walled or large products.

[0005] Traditional thermoplastic composite molding dies often have an integrated heating and cooling zone structure. The cooling zone is not used to heat the composite material blank, and the heating and cooling zones heat up together during the heating process, resulting in low heating efficiency and energy waste. When dissipating heat, the high temperature (heat) of the composite material product in the mold and the heating zone needs to be conducted to the cooling zone first, and then dissipated to the external environment, resulting in low cooling efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a cold mold-hot pressing mold and thermoplastic composite materials. Independent heating and cooling devices are installed in both the upper and lower molds, and an insulation layer is used to isolate them, achieving physical separation of the heating and cooling areas of the mold. This prevents heat conduction from the heating area to the cooling area, reducing heat loss to the cooling area during product heating and heat preservation, thus achieving energy-saving effects. Furthermore, the invention utilizes a medium-transfer cooling technology to achieve rapid heat dissipation from the mold heating area, improving the heating and cooling efficiency of the product, reducing product production cycle time, and ensuring molding quality.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, a cold mold-hot pressing forming mold includes an upper mold and a lower mold, wherein the upper mold and the lower mold are respectively provided with a corresponding upper mold forming surface and a lower mold forming surface; On the side of the upper mold forming surface away from the lower mold, an upper mold heating section, an upper mold insulation section, and an upper mold cooling section are arranged in sequence. The upper mold heating section is provided with a heating element and a first medium flow channel. The first medium flow channel is arranged around the heating element. The upper mold cooling section is provided with a second medium flow channel. The first medium flow channel and the second medium flow channel are connected through an upper mold control pipeline. The upper mold control pipeline is arranged in the upper mold insulation section, and a valve assembly is provided on the upper mold control pipeline. On the side of the lower mold forming surface away from the upper mold, a lower mold heating section, a lower mold insulation section, and a lower mold cooling section are arranged sequentially. The lower mold heating section is provided with a heating element and a third medium flow channel, which is located around the heating element. The lower mold cooling section is provided with a fourth medium flow channel. The third medium flow channel and the fourth medium flow channel are connected through a lower mold control pipeline. The lower mold control pipeline is located in the lower mold insulation section, and a valve assembly is provided on the lower mold control pipeline.

[0008] Secondly, a method for preparing a thermoplastic composite material based on the above-mentioned cold mold-hot pressing mold includes the following steps: At room temperature, a thermoplastic composite prepreg is laid on the molded surface to obtain a prepreg. After the prepreg is pre-compacted, a release film and a breathable felt are set in sequence and sealed with a vacuum bag. The vacuum bag is then connected to an air extraction pipeline and a vacuum is drawn inside the vacuum bag. Press the upper mold forming surface onto the vacuum bag, close the valve assembly in the upper and lower molds, start the heating element to heat according to the set heating sequence, and after reaching the set target temperature, apply forming pressure to the preform in the vacuum bag through the upper and lower molds, and maintain pressure to remove air and impregnate for forming. Open the valve assemblies in the upper and lower molds to allow the low-temperature medium in the second medium channel to replace the high-temperature medium in the first medium channel, and the low-temperature medium in the fourth medium channel to replace the high-temperature medium in the third medium channel, thereby cooling the mold and the molded component.

[0009] The beneficial effects of this invention are as follows: The device of the present invention has heat insulation sections provided between the cooling section and the heating section in the upper and lower molds, respectively. When the heating section is at a high temperature and the cooling section is at a low temperature, the heat exchange between the two can be prevented by the heat insulation section and the valve assembly in the heat insulation section, thereby maintaining the heat transfer from the heating section to the blank during the heating process. When cooling, the valve assembly is opened, and a low temperature medium can be transported to the heating section to achieve rapid cooling of the mold, avoiding thermal inertia and heat loss during the long cooling process, thus achieving the effects of energy saving and improving production efficiency. Attached Figure Description

[0010] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0011] Figure 1 This is a schematic diagram of the cold mold-hot pressing mold in Example 1.

[0012] Among them, 10, upper mold; 11, upper mold cooling section; 111, second medium flow channel; 12, upper mold insulation section; 121, upper mold valve assembly; 13, upper mold heating section; 131, upper mold heating element; 132, first medium flow channel; 14, upper mold forming surface; 141, upper mold positioning structure; 20, lower mold; 21, lower mold cooling section; 211, fourth medium flow channel; 22, lower mold insulation section; 221, lower mold valve assembly; 23, lower mold heating section; 231, lower mold heating element; 232, third medium flow channel; 24, lower mold forming surface; 241, lower mold positioning structure; 40, vacuum sealing system; 41, vacuum bag; 42, breathable felt; 43, isolation film; 44, preform. Detailed Implementation

[0013] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0014] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0015] One or more embodiments of the present invention provide a cold mold-hot pressing forming mold, including an upper mold and a lower mold, wherein the upper mold and the lower mold are respectively provided with opposing upper mold forming surfaces and lower mold forming surfaces; On the side of the upper mold forming surface away from the lower mold, an upper mold heating section, an upper mold insulation section, and an upper mold cooling section are arranged in sequence. The upper mold heating section is provided with a heating element and a first medium flow channel. The first medium flow channel is arranged around the heating element. The upper mold cooling section is provided with a second medium flow channel. The first medium flow channel and the second medium flow channel are connected through an upper mold control pipeline. The upper mold control pipeline is arranged in the upper mold insulation section, and a valve assembly is provided on the upper mold control pipeline. On the side of the lower mold forming surface away from the upper mold, a lower mold heating section, a lower mold insulation section, and a lower mold cooling section are arranged sequentially. The lower mold heating section is provided with a heating element and a third medium flow channel, which is located around the heating element. The lower mold cooling section is provided with a fourth medium flow channel. The third medium flow channel and the fourth medium flow channel are connected through a lower mold control pipeline. The lower mold control pipeline is located in the lower mold insulation section, and a valve assembly is provided on the lower mold control pipeline.

[0016] In the above structure, the upper and lower molds are symmetrically arranged with a forming surface, a heating section, an insulating section, and a cooling section. The forming surface constrains the surface shape of the formed component. No flow channels or heating elements are located inside the forming surface, which is detachably connected to the heating section. The forming surface can be replaced with a different shape depending on the shape of the formed component. The heating section is directly connected to the forming surface and contains a first or third medium flow channel surrounding the heating element. When the heating element heats up, the heat first heats the medium in the medium flow channel, causing the entire heating section to heat up, and then the heat is transferred to the forming surface to heat the formed component. The insulating section is located between the heating and cooling sections and has extremely low thermal conductivity. It prevents heat conduction between the heating and cooling sections, allowing heat to be transferred only through the medium flowing in the control pipeline. When the valve assembly is closed, heat transfer between the heating and cooling sections is impossible, maximizing heat transfer to the formed component and achieving energy savings. Since the heat exchange between the heating element and the outside world is mainly achieved by the medium in the medium flow channel, the temperature level of the heating element can be quickly adjusted by replacing the medium in the medium flow channel, thereby achieving precise temperature control and avoiding heat loss caused by the thermal inertia of the mold and performance degradation caused by slow cooling rate.

[0017] Optionally, an upper mold positioning structure is provided on the upper mold forming surface, and a lower mold positioning structure is provided on the lower mold forming surface; the upper mold positioning structure and the lower mold positioning structure are shaped to match each other; for example, positioning pins, positioning grooves, guide grooves, locking bolts and buckles are used to achieve precise positioning between the upper and lower molds and ensure the shape accuracy of the formed component.

[0018] Optionally, the heating element is an armored electric heating tube, used to heat the medium in the peripheral medium flow channel.

[0019] Optionally, the second medium flow channel and the fourth medium flow channel are respectively connected to a cooling device; the cooling device includes a cooling pool located outside the mold equipment, which can further cool down the high-temperature medium quickly and recover heat.

[0020] Optionally, in the upper mold cooling section, the second medium flow channel is arranged in a tortuous manner, including multiple parallel pipes, which increases the heat exchange area between the medium and the cooling section, which is conducive to rapid heat exchange between the hot medium and the cooling section, achieving the purpose of rapid cooling of the mold, and also helps to achieve the weight reduction of the mold.

[0021] Optionally, in the lower mold cooling section, the fourth medium flow channel is arranged in a tortuous manner, including multiple parallel pipes, which increases the heat exchange area between the medium and the cooling section, which is conducive to rapid heat exchange between the hot medium and the cooling section, achieving the purpose of rapid cooling of the mold, and also helps to achieve the weight reduction of the mold.

[0022] Optionally, the upper mold forming surface, lower mold forming surface, upper mold heating part, lower mold heating part, upper mold cooling part, and lower mold cooling part are all made of thermally conductive metal. Specifically, the upper mold forming surface and lower mold forming surface are made of mold steel, with finely machined and polished surfaces, and surface treated (with a Teflon coating) to facilitate demolding. The upper mold heating part and lower mold heating part are made of high-strength mold steel, which can maintain high strength after the internal cavity and flow channel are prepared to ensure molding pressure. The upper mold cooling part and lower mold cooling part are made of high-strength mold steel or aluminum alloy with good heat dissipation. The upper mold insulation part and lower mold insulation part are made of alumina aerogel felt.

[0023] Optionally, in the cold mold-hot pressing molding die, the heating element and valve assembly are respectively connected to the control system, which can adjust the start and stop of the heating element and the on and off of the valve assembly based on the detected molding surface temperature, so as to ensure that the mold controls the temperature, pressure and time in a coordinated manner according to the preset process curve.

[0024] One or more embodiments of the present invention provide a method for preparing thermoplastic composite materials based on the above-mentioned cold mold-hot pressing mold, comprising the following steps: At room temperature, a thermoplastic composite prepreg is laid on the molded surface to obtain a prepreg. After the prepreg is pre-compacted, a release film and a breathable felt are set in sequence and sealed with a vacuum bag. The vacuum bag is then connected to an air extraction pipeline and a vacuum is drawn inside the vacuum bag. Press the upper mold forming surface onto the vacuum bag, close the valve assembly in the upper and lower molds, start the heating element to heat according to the set heating sequence, and after reaching the set target temperature, apply forming pressure to the preform in the vacuum bag through the upper and lower molds, and maintain pressure to remove air and impregnate for forming. Open the valve assemblies in the upper and lower molds to allow the low-temperature medium in the second medium channel to replace the high-temperature medium in the first medium channel, and the low-temperature medium in the fourth medium channel to replace the high-temperature medium in the third medium channel, thereby cooling the mold and the molded component.

[0025] In the above process, the replacement of the high-temperature medium in the heating section with the low-temperature medium achieves rapid cooling of the heating section, thereby enabling the molded component to cool rapidly to below the glass transition temperature under pressure, ensuring its toughness and impact resistance, and quickly entering the next production cycle.

[0026] Optionally, after opening the valve assemblies in the upper and lower molds, the high-temperature medium in the first medium flow channel is transported to the cooling device through the second medium flow channel, and the high-temperature medium in the third medium flow channel is transported to the cooling device through the fourth medium flow channel; the medium is rapidly cooled and the heat is recovered and reused in the cooling device.

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Example 1 A cold mold-hot pressing mold, such as Figure 1 As shown, it includes an upper mold 10 and a lower mold 20, with the upper mold 10 and the lower mold 20 respectively provided with opposing upper mold forming surfaces 14 and lower mold forming surfaces 24; On the side of the upper mold forming surface 14 away from the lower mold 20, an upper mold heating part 13, an upper mold insulation part 12, and an upper mold cooling part 11 are arranged in sequence. The upper mold heating part 13 is provided with an upper mold heating element 131 and a first medium flow channel 132. The first medium flow channel 132 is located around the upper mold heating element 131. The upper mold cooling part 11 is provided with a second medium flow channel 111. The first medium flow channel 132 and the second medium flow channel 111 are connected through an upper mold control pipeline. The upper mold control pipeline is located in the upper mold insulation part 12, and an upper mold valve assembly 121 is provided on the upper mold control pipeline. Since multiple upper mold control pipelines are arranged between the first medium flow channel 132 and the second medium flow channel 111 to realize the medium flow, an upper mold valve assembly 121 is provided on each upper mold control pipeline. On the side of the lower mold forming surface 24 away from the upper mold 10, a lower mold heating section 23, a lower mold insulation section 22, and a lower mold cooling section 21 are arranged in sequence. The lower mold heating section 23 is provided with a lower mold heating element 231 and a third medium flow channel 232. The third medium flow channel 232 is located around the lower mold heating element 231. The lower mold cooling section 21 is provided with a fourth medium flow channel 211. The third medium flow channel 232 and the fourth medium flow channel 211 are connected by a lower mold control pipeline. The lower mold control pipeline is located in the lower mold insulation section 22, and a lower mold valve assembly 221 is provided on the lower mold control pipeline. Since multiple lower mold control pipelines are provided between the third medium flow channel 232 and the fourth medium flow channel 211 to realize the flow of medium, a lower mold valve assembly 221 is provided on each lower mold control pipeline.

[0029] An upper mold positioning structure 141 is provided on the upper mold forming surface 14, and a lower mold positioning structure 241 is provided on the lower mold forming surface 24. The upper mold positioning structure 141 and the lower mold positioning structure 241 are positioning pins and positioning grooves with mutually matching shapes, which are used to achieve precise positioning between the upper and lower molds.

[0030] The upper mold heating element 131 and the lower mold heating element 231 are armored electric heating tubes, which are used to heat the medium in the peripheral medium flow channel.

[0031] The second medium flow channel 111 and the fourth medium flow channel 211 are respectively connected to the cooling device; the cooling device includes a cooling pool located outside the mold equipment, which can further realize the rapid cooling of the high-temperature medium and the recovery and utilization of heat.

[0032] In the upper mold cooling section 11, the second medium flow channel 111 is arranged in a tortuous manner and includes multiple parallel pipes; in the lower mold cooling section 21, the fourth medium flow channel 211 is arranged in a tortuous manner and includes multiple parallel pipes.

[0033] The upper mold forming surface 14 and the lower mold forming surface 24 are made of mold steel, with fine machining and polishing. Surface treatment (such as Teflon coating) is used to facilitate demolding. The upper mold heating part 13 and the lower mold heating part 23 are made of high-strength mold steel, which can maintain high strength after the internal cavity and flow channel are prepared to ensure molding pressure. The upper mold cooling part 11 and the lower mold cooling part 21 are made of high-strength mold steel with good heat dissipation. The upper mold insulation part 12 and the lower mold insulation part 22 are made of alumina aerogel felt.

[0034] In the cold mold-hot pressing molding die, the upper mold heating element 131, the lower mold heating element 231, the upper mold valve assembly 121 and the lower mold valve assembly 221 are respectively connected to the control system, which can adjust the start and stop of the heating element and the on and off of the valve assembly based on the detected molding surface temperature, so as to ensure that the mold controls the temperature, pressure and time in a coordinated manner according to the preset process curve.

[0035] The method for preparing thermoplastic composite materials based on the cold mold-hot pressing mold in this embodiment includes the following steps: Under normal temperature conditions, thermoplastic composite prepreg is laid on the molded surface 24 to obtain a prepreg body 44. After the prepreg body 44 is pre-compacted, a release film 43 and a breathable felt 42 are set in sequence and sealed with a vacuum bag 41. The vacuum bag 41 is connected to the air extraction pipeline and the vacuum bag 41 is evacuated to obtain a vacuum sealing system 40. Press the upper mold forming surface 14 onto the vacuum sealing system 40, close the valve assembly in the upper mold 10 and lower mold 20, start the upper mold heating element 131 and lower mold heating element 231 to heat in the set heating sequence, and after reaching the set target temperature, apply forming pressure to the layup blank 44 in the vacuum sealing system 40 through the upper mold 10 and lower mold 20, and maintain pressure, vent air, and impregnate to form. Open the upper mold valve assembly 121 and the lower mold valve assembly 221 to allow the low-temperature medium in the second medium flow channel 111 to replace the high-temperature medium in the first medium flow channel 132, and allow the low-temperature medium in the fourth medium flow channel 211 to replace the high-temperature medium in the third medium flow channel 232, thereby cooling the mold and the molded component.

[0036] After opening the upper mold valve assembly 121 and the lower mold valve assembly 221, the high-temperature medium in the first medium flow channel 132 is transported to the cooling device through the second medium flow channel 111, and the high-temperature medium in the third medium flow channel 232 is transported to the cooling device through the fourth medium flow channel 211; the medium is rapidly cooled and the heat is recovered and reused in the cooling device.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cold mold-hot pressing forming mold, characterized in that, It includes an upper mold and a lower mold, with corresponding upper mold forming surfaces and lower mold forming surfaces respectively. On the side of the upper mold forming surface away from the lower mold, an upper mold heating section, an upper mold insulation section, and an upper mold cooling section are arranged in sequence. The upper mold heating section is provided with a heating element and a first medium flow channel. The first medium flow channel is arranged around the heating element. The upper mold cooling section is provided with a second medium flow channel. The first medium flow channel and the second medium flow channel are connected through an upper mold control pipeline. The upper mold control pipeline is arranged in the upper mold insulation section, and a valve assembly is provided on the upper mold control pipeline. On the side of the lower mold forming surface away from the upper mold, a lower mold heating section, a lower mold insulation section, and a lower mold cooling section are arranged sequentially. The lower mold heating section is provided with a heating element and a third medium flow channel, which is located around the heating element. The lower mold cooling section is provided with a fourth medium flow channel. The third medium flow channel and the fourth medium flow channel are connected through a lower mold control pipeline. The lower mold control pipeline is located in the lower mold insulation section, and a valve assembly is provided on the lower mold control pipeline.

2. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, An upper mold positioning structure is provided on the upper mold forming surface, and a lower mold positioning structure is provided on the lower mold forming surface; the shapes of the upper mold positioning structure and the lower mold positioning structure are mutually compatible.

3. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, The heating element is an armored electric heating tube.

4. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, The second medium flow channel and the fourth medium flow channel are respectively connected to the cooling device.

5. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, In the upper mold cooling section, the second medium flow channel is distributed in a tortuous manner.

6. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, In the lower mold cooling section, the fourth medium flow channel is distributed in a tortuous manner.

7. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, The upper mold forming surface, lower mold forming surface, upper mold heating part, lower mold heating part, upper mold cooling part and lower mold cooling part are all made of thermally conductive metal, and the upper mold insulation part and lower mold insulation part are made of alumina aerogel felt.

8. The cold mold-hot pressing forming mold as described in claim 1, characterized in that, The heating element and valve assembly are respectively connected to the control system, which can adjust the start and stop of the heating element and the on / off state of the valve assembly based on the detected temperature of the molding surface.

9. A method for preparing a thermoplastic composite material based on a cold mold-hot pressing mold as described in any one of claims 1-8, characterized in that, Including the following steps: At room temperature, a thermoplastic composite prepreg is laid on the molded surface to obtain a prepreg. After the prepreg is pre-compacted, a release film and a breathable felt are set in sequence and sealed with a vacuum bag. The vacuum bag is then connected to an air extraction pipeline and a vacuum is drawn inside the vacuum bag. Press the upper mold forming surface onto the vacuum bag, close the valve assembly in the upper and lower molds, start the heating element to heat according to the set heating sequence, and after reaching the set target temperature, apply forming pressure to the preform in the vacuum bag through the upper and lower molds, and maintain pressure to remove air and impregnate for forming. Open the valve assemblies in the upper and lower molds to allow the low-temperature medium in the second medium channel to replace the high-temperature medium in the first medium channel, and the low-temperature medium in the fourth medium channel to replace the high-temperature medium in the third medium channel, thereby cooling the mold and the molded component.

10. The method for preparing thermoplastic composite materials as described in claim 9, characterized in that, After opening the valve assemblies in the upper and lower molds, the high-temperature medium in the first medium flow channel is transported to the cooling device through the second medium flow channel, and the high-temperature medium in the third medium flow channel is transported to the cooling device through the fourth medium flow channel.

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